The lowest overall recession occurred in reach C--the result of the lake- 

 ward movement of the foredune in the second period. If the stations where the 

 accretion occurred are not included, then the overall retreat rate increases 

 from 2.4 to 3.2 meters per year, very close to the overall rate for reach E of 

 3.5 meters per year. Even though the bluff recession rate for reach C was low, 

 the rate of shoreline change was the third highest, averaging -3.7 meters per 

 year. Most of this shoreline movement occurred during the first period. 



The changes during the second period are difficult to interpret. In gen- 

 eral, the recession rate peaked during this period and then decreased in the 

 final year. This did not, however, occur in reach C where the bluff at the 

 southern end accreted, thereby reducing the average recession rate! 



The lowest rates of both shoreline change and bluff recession occurred 

 between the fall of 1973 and November 1974 with similar recession rates along 

 reaches A, B, and D and in reaches C and E. Interestingly, the average reces- 

 sion rate along reach B, even with the long seawall in place, slightly exceeded 

 the reach A rate. Average recession for all reaches over the full period was 

 13.6 meters for a rate of 3.8 meters per year. The associated shoreline change 

 was slightly less. 



Comparing the recession rates north and south of the powerplant, the rates 

 were higher (to the north) in the first period (April 1971 to November 1972), 

 lower in the second period (November 1972 to October or November 1973) and 

 about equal in the third period (October or November 1973 to November 1974) . 

 In view of the different characteristics of the reaches, these differences 

 (positive and negative) are insignificant and it is unlikely that they can be 

 attributed to the construction of the temporary harbor. This agrees with the 

 findings reported by Johnson and Hiipakka (1976). 



2. Previous Berrien County Erosion Studies . 



Numerous studies have been conducted on Great Lakes shorelines. Primary 

 topics include studies of geomorphology, sediment characteristics, and bluff 

 or shoreline changes. A number of these studies have dealt with bluff reces- 

 sion in Berrien County. 



A comprehensive study by Powers (1958) classified the entire Lake Michigan 

 shoreline according to geomorphology (bluff type, composition, and height). He 

 also relocated section lines where old bluff- line measurements had been made 

 and determined the rate of bluff retreat. Of 134 stations around the lake. 

 Powers reported that 124 eroded an average of 0.45 meter per year, 4 had no 

 change, and the remaining 6 accreted an average of 0.48 meter per year. 

 Periods of coverage varied from 20 to 12 7 years. 



Powers also recognized lake level fluctuations, severe storms, and manmade 

 structures as primary factors affecting the recession rate. However, he noted 

 the paucity of measurements needed to quantify the relationship between lake 

 level and bluff recession. 



Powers (1958) reported that the shoreline in Berrien County consisted pri- 

 marily of 3- to 12-meter-high bluffs and 6- to 38-meter-high dunes, that the 

 beaches averaged 9 to 49 meters wide, and that the average bluff recession 



50 



